CVE-2025-21970

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5: Bridge, fix the crash caused by LAG state check

When removing LAG device from bridge, NETDEVCHANGEUPPER event is triggered. Driver finds the lower devices (PFs) to flush all the offloaded entries. And mlx5lagissharedfdb is checked, it returns false if one of PF is unloaded. In such case, mlx5eswbridgelagrepget() and its caller return NULL, instead of the alive PF, and the flush is skipped.

Besides, the bridge fdb entry's lastuse is updated in mlx5 bridge event handler. But this SWITCHDEVFDBADDTOBRIDGE event can be ignored in this case because the upper interface for bond is deleted, and the entry will never be aged because lastuse is never updated.

To make things worse, as the entry is alive, mlx5 bridge workqueue keeps sending that event, which is then handled by kernel bridge notifier. It causes the following crash when accessing the passed bond netdev which is already destroyed.

To fix this issue, remove such checks. LAG state is already checked in commit 15f8f168952f ("net/mlx5: Bridge, verify LAG state when adding bond to bridge"), driver still need to skip offload if LAG becomes invalid state after initialization.

Oops: stack segment: 0000 [#1] SMP CPU: 3 UID: 0 PID: 23695 Comm: kworker/u40:3 Tainted: G OE 6.11.0mlnx #1 Tainted: [O]=OOTMODULE, [E]=UNSIGNEDMODULE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Workqueue: mlx5bridgewq mlx5eswbridgeupdatework [mlx5core] RIP: 0010:brswitchdevevent+0x2c/0x110 [bridge] Code: 44 00 00 48 8b 02 48 f7 00 00 02 00 00 74 69 41 54 55 53 48 83 ec 08 48 8b a8 08 01 00 00 48 85 ed 74 4a 48 83 fe 02 48 89 d3 <4c> 8b 65 00 74 23 76 49 48 83 fe 05 74 7e 48 83 fe 06 75 2f 0f b7 RSP: 0018:ffffc900092cfda0 EFLAGS: 00010297 RAX: ffff888123bfe000 RBX: ffffc900092cfe08 RCX: 00000000ffffffff RDX: ffffc900092cfe08 RSI: 0000000000000001 RDI: ffffffffa0c585f0 RBP: 6669746f6e690a30 R08: 0000000000000000 R09: ffff888123ae92c8 R10: 0000000000000000 R11: fefefefefefefeff R12: ffff888123ae9c60 R13: 0000000000000001 R14: ffffc900092cfe08 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88852c980000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f15914c8734 CR3: 0000000002830005 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> ? _diebody+0x1a/0x60 ? die+0x38/0x60 ? dotrap+0x10b/0x120 ? doerrortrap+0x64/0xa0 ? excstacksegment+0x33/0x50 ? asmexcstacksegment+0x22/0x30 ? brswitchdevevent+0x2c/0x110 [bridge] ? schedbalancenewidle.isra.149+0x248/0x390 notifiercallchain+0x4b/0xa0 atomicnotifiercallchain+0x16/0x20 mlx5eswbridgeupdate+0xec/0x170 [mlx5core] mlx5eswbridgeupdatework+0x19/0x40 [mlx5core] processscheduledworks+0x81/0x390 workerthread+0x106/0x250 ? bhworker+0x110/0x110 kthread+0xb7/0xe0 ? kthreadpark+0x80/0x80 retfromfork+0x2d/0x50 ? kthreadpark+0x80/0x80 retfromfork_asm+0x11/0x20 </TASK>